How should you go around with geometry for Unity?
Better for what?  The only thing that matters is the outcome.  If either model does everything you want, then either model is the correct one.

You don't need to ask anybody which of two models you have made is better.  Just hit F12.

I will say that there are probably a few issues with these models.  But the issues depend on how you're going to use them.  Are they supposed to be smooth shaded?  Auto-smooth?  Are you going to have UV mapped textures, vertex color?  Are they going to deform?  Are you going to share the models for others to edit, or are they just for animation?  Are they for use in Blender or in a different engine?

If you are using Blender to render, and you are using sharp edges /autosmooth / flat shading, and you are using split vertices for all potentially interpolated values like vertex color and UV, and you are done with the mesh and do not plan to deform it or use it to deform any other mesh, or to use it for any physics, and you're not going to use Catmull-Clark subdivision, (whew I'm out of breath), then there is nothing wrong with either model.  But the second shouldn't be seen as superior to the first model, just adequate.

Because both models have ngons, the biggest difference between the two is that the second has a concave face, which will give you problems with use with some modifiers.

If any of that long list of things I mentioned doesn't apply, then you've got issues with both models.  Use more control loops or practice your topology, avoid ngons.